The present invention relates to an improved metalworking vise, and more particularly relates to improvement in construction of a clamp force amplifying mechanism used for a metalworking vise.
In general construction of a metalworking vise, a stationary jaw is amounted to a fixed base arranged on a work table of a machine, a horizontal screw drive shaft is axially rotatablly mounted to the fixed base and a slide jaw mounted to the screw drive shaft via an integral nut is arranged facing the fixed jaw. On rotation of the screw drive shaft, the slide jaw is driven for movement towards the stationary jaw in order to clamp a workpiece in between.
In this specification words "front" and "forward" are used in connection with the stationary jaw side whereas words "rear" and "rearwards" are used in connection with the slide jaw side.
Since the above-described construction is unable to generate clamp force of sufficient magnitude, use of a force magnifying mechanism in the construction of a metalworking vise is already proposed. The construction disclosed in Japanese Patent Publication No. Sho. 63-41711 is one example, in which an oil pressure chamber is provided within a shaft coupled to a slide jaw and this shaft encases a piston slidable towards the oil pressure chamber. In clamping operation, the piston is screw driven to intrude into the oil chamber to raise its oil pressure and the slide jaw is moved forwards with a large force via application of oil pressure to the shaft end. Japanese Patent Laid-Open No. Sho. 61-95881 also proposes use of a force magnifying mechanism in construction of a metalworking vise.
In the case of these conventional proposals, however, the force magnifying mechanisms is located on the upstream side of the slide jaw along the clamping direction. Due to this location of the force magnifying mechanism, clamping operation of a workpiece poses a counter force, which is generated as a reaction of the clamp force, onto the rear end face of the fixed base. This counter force causes undesirable warping of the fixed base, which inevitably lowers precision in clamping position. In particular, use of a force magnifying mechanism generates a large counter force and, as a consequence, increased warping of the fixed base. In addition, it is necessary to arrange an additional member at the rear end of the fixed base to endure the increased counter force and presence of such an additional member naturally results in an increased size of the entire construction. Further presence of such an additional member at the rear end of the fixed base limits sliding ambit of the slide jaw and, accordingly, the size of workpieces to be worked on the vise.